1. Field of the Invention
The present invention relates generally to active vehicle suspension systems and more particularly to a system and method for enhancing an active vehicle suspension system by sensing the engagement of obstacles or uneven ground and adjusting the suspending actuator forces to reduce the amount of drive energy otherwise required to overcome the ground/pathway anomaly and move the vehicle forward while at the same time maintaining the stability of the vehicle.
2. Description of the Prior Art
In conventional vehicle suspension systems various types of springs and associated shock absorbing devices have historically been the primary components used to exert supporting forces between the chassis and wheels in order to provide vehicle stability and ride comfort. More recently, active and partially active (hybrid) suspension systems include actuators controlled by a microprocessor to provide these forces.
The benefit of active suspension systems exploited in the prior art has primarily been related to controlling the actuator forces for the purpose of improving vehicle ride comfort and control.
The present invention focuses on a separate and distinct benefit of the use of active vehicle suspension methodology to indirectly manage the power required to overcome ground/pathway anomalies; namely, the enhancement of an active suspension system for the primary purpose of shifting and adjusting the supporting actuator forces to reduce the amount of drive energy otherwise required to move a vehicle forward in uneven terrain environments including ground/pathway anomalies such as a bump, depression, boulder, ravine, ramp, etc., or any combination thereof.
Reducing the drive energy otherwise required to move a vehicle forward will provide the added benefit of enabling the vehicle to continue forward movement in hostile terrain environments where previously forward movement may have been difficult or impossible due to drive energy requirements being greater than the available drive energy or the wheel traction with the engaged terrain would allow.
In a conventional vehicle suspension system, i.e., one that uses passive springs at each wheel to exert a majority of the supporting force between the chassis and the wheels, as the vehicle travels over uneven terrain the wheels move up and down in relation to the vehicle chassis as the characteristics of the ground, roadway or other vehicle pathway change. In an extreme example, such as a rocky landscape, a large rock, or an extreme pathway anomaly or obstacle is engaged by one wheel, that wheel will move up towards the chassis (compressing the corresponding suspension element) or down away from the chassis (extending the suspension element), and the diametrically opposite wheel will move in the same direction up or down (relative to the chassis), while the two adjacent wheels will tend to move in the opposite direction down or up (extending or compressing their suspension elements).
In this example, a conventional suspension system using passive springs, the spring force pushing down on the two compressed springs will be relatively large, and the spring forces of the two extended springs will be relatively small. For ease of explanation, spring force will be referred to herein as pushing the wheel down (against the ground or other pathway surface), as opposed to pushing the chassis up. In the conventional suspension scenario of a vehicle moving over uneven terrain, any suspension element that is compressed will push downward with relatively large force and any suspension element that is extended will push downward with relatively small force; such is the operative nature of a spring.
As the vehicle travels over this type of uneven terrain, each wheel will also see varying angles of approach to bumps, rocks, ravines, crevices or other pathway anomalies encountered. For example, a wheel traveling up a rock will have a positive angle of approach (O/), a wheel traveling down a rock, or into a depression, will have a negative angle of approach (\O), and a wheel remaining on flat ground will have a zero angle (O). At a given time, one, two or three wheels might have a positive angle of approach while the others might have zero or negative angles of approach.
Envision the right front wheel of a vehicle beginning to compress its suspension as it engages and travels over a large rock. Half way up the rock the suspension will be pushing down with a relatively large force due to its partial compression. It might also have a large positive angle of approach due to the rock being in front of it. It is easy to see that in this scenario it becomes relatively difficult for this wheel to travel forward. The greater the angle of approach (steeper the facing side of the rock) and the greater the downward force (the more compressed the spring is), the more drive energy it will take to move the wheel forward and up the face of the rock. Because the rock presents an impediment to forward movement, the total energy required to move the vehicle forward will thus be equal to the additional drive energy required to move this right front wheel forward in overcoming the impediment plus the energy required to move the other three wheels forward.
Now consider a similar situation in which the vehicle has an active suspension system wherein computer processor controlled actuators are provided at each wheel to exert selective supporting forces between the chassis and each wheel. The benefits of active suspension systems exploited in the prior art have primarily been related to improved vehicle ride comfort and control, not reduction of required drive energy or improvement in drive efficiency and functionality in situations where impediments to forward motion or other pathway anomalies are encountered.
It is therefore a principal objective of the present invention to provide an improved active vehicle suspension system and methodology in which ground/pathway anomalies are sensed, and chassis supporting actuator forces are adjusted to reduce the drive energy otherwise required to move the vehicle forward over the ground/pathway anomalies.
Another objective of the present invention is to provide an improved active vehicle suspension system and methodology in which chassis supporting actuator forces are adjusted in a coordinated and balanced manner, and applied to the wheels in a coordinated and balanced manner to reduce the drive energy otherwise required to move the vehicle forward over pathway anomalies.
Still another objective of the present invention is to provide an improved active vehicle suspension system and methodology in which chassis supporting actuator forces are adjusted in a coordinated and balanced manner following a defined set of rules that prevents unwonted chassis movement as a result of the supporting actuator force adjustments made to reduce the drive energy otherwise required to move the vehicle forward over pathway anomalies.
Yet another objective of the present invention is to provide an improved active vehicle suspension system and methodology in which the slope values of the terrain or pathway relative to the vehicle chassis in the direction of vehicle movement at the points of contact between each vehicle wheel and the ground/pathway are estimated and then used to purposefully shift chassis supporting actuator forces among the several chassis supporting actuators in order to reduce the drive energy otherwise required to move the vehicle forward over the ground/pathway anomalies.